1. Field of the Invention
The present invention relates to a device for producing an annular or arcuate magnet, by which an annular or arcuate preformed body is formed from a compound containing anisotropic magnet powder, the magnetic field of the preformed body is oriented, and pressure is applied thereto.
2. Description of Related Art
There has been employed a method of forming a compound obtained by mixing the anisotropic magnet powder and a thermosetting resin to produce a magnetically anisotropic resin bonded magnet. With the process disclosed in Japanese Patent No. 2816668, for example, the above-described compound is charged in a preforming mold which has been heated, a magnetic field is applied to the compound to orient anisotropic magnet powder in a prescribed direction, thereby orienting the magnetic field thereof, and at the same time, pressure is applied to the compound to form a preformed body. Then, the preformed body is placed in a main forming mold that has been heated, and a pressure larger than that upon preforming is further applied to the preformed body for compression thereof, thereby forming the above-described magnet.
As described above, by forming a preformed body previously, and then compressing the preformed body with a larger pressing force, a magnet with excellent dimensional accuracy can be produced.
However, further improvement of the dimensional accuracy of the above-described magnet, and reduction of the scattering in mass thereof greatly depend on the charging amount of the compound in the preforming mold. And, in particular, where an annular magnet with an annular configuration or an arcuate magnet with an arcuate configuration is produced, a cavity in the preforming mold, which is adapted to charge the above-described compound, becomes narrow to make the uniform charging of this compound difficult.
Consequently, upon producing the annular magnet or arcuate magnet with the process of Japanese Patent No. 2816668, the mass along with the magnet performance thereof may scatter.